The RFI’s premise is that movement toward standards-based COTS modular solutions will fix fragmentation, variability, and lock-in. My experience says the causality mostly runs the other way: fragmentation, variability, and lock-in are produced by the conditions under which states buy and build, and COTS purchased under those same conditions reproduces the same results with a different logo. The most damaging pattern is buying COTS as a forcing function to standardize business processes around vendor constraints rather than mission requirements. It consistently produces poor outcomes and governments locked into costly solutions, which is a condition the RFI seeks to avoid.
There is also a timing consideration, developed fully in S4: software build economics are shifting fast enough that a standards program hard-coding the current COTS landscape as its target state will be standardizing on a ceiling that is about to become a floor. Emerging standards worth watching (question SE-1) matter less than emerging build economics.